Patent Grant
9783395
The disclosed subject matter relates to systems and methods for positioning a moveably counterweight on a crane.
The present application relates to lift cranes, and particularly to mobile lift cranes having a counterweight that can be moved to different positions in an effort to balance a load on the crane.
Lift cranes typically include counterweights to help balance the crane when the crane lifts a load. Since the load is often moved in and out with respect to the center of rotation of the crane, and thus generates different moments throughout a crane pick, move and set operation, it is advantageous if the counterweight, including any extra counterweight attachments, can also be moved forward and backward with respect to the center of rotation of the crane. In this way a smaller amount of counterweight can be utilized than would be necessary if the counterweight had to be kept at a fixed distance.
However, when there is no load on the hook, it is necessary to make sure that the counterweight is not in position to tip the crane backwards. Thus, if the crane needs to move without a load on the hook, the extra counterweight attachment must be close enough to the body. Additionally, safety codes may limit the distance and amount of counterweight used to prevent tipping in the case of loss of load. Thus for maximum lifting capacity, the counterweight may be extended as far as possibly while complying with general safety concerns and safety regulations which limit the extent that a counter weight may be extended from the crane.
Current systems generally position the counterweight as far away from the crane body as possible for a given boom configuration, while maintaining compliance with safety regulations or other concerns. With the counterweights in this position, the crane is at its maximum lifting capacity for the amount of counterweights present. Based on maximizing capacity alone, there is no reason why the counterweight would ever need to be positioned less than the maximum allowable extension.
In one aspect, a method for positioning a counterweight of a crane includes determining a boom orientation, determining a first counterweight position corresponding to a first rearward stability associated with the boom orientation, determining a first crane capacity at the first counterweight position, determining a second counterweight position corresponding to a second rearward stability associated with the boom orientation, determining a second crane capacity at the second counterweight position, determining a load of the crane, and positioning the counterweight at a third position between the first counterweight position and the second counterweight position dependent on the boom load, and the first crane capacity.
In some embodiments, the method further includes determining the load changing to a new load, and moving the counterweight to a fourth position between the first counterweight position and the second counterweight position dependent on the new load, and the first crane capacity. In some embodiments, the load corresponds to a set percentage of the first crane capacity and a third crane capacity associated with the third position and the new load corresponds to the same set percentage of a fourth crane capacity associated with the fourth position.
In some embodiments, the load comprises a boom strap tension. In some embodiments, the load is a boom hoist tension. In some embodiments, the load is a compression of a gantry. In some embodiments, the load is a moment between an upperworks and a lower works of a crane. In some embodiments, the load is a moment between a crane carbody and a crane crawler. In some embodiments, the load is a ground pressure associated with a crane outrigger.
In another aspect, a system for controlling the position of an counterweight on a crane includes an actuator configured to change a horizontal position of a counterweight relative to a crane body, a sensor configured to measure a crane load, and a controller in communication with the actuator, the sensor, and the input. The controller is configured to perform functions including determine a boom orientation, determine a first counterweight position corresponding to a first rearward stability associated with the determined boom orientation, determine a first crane capacity at the first counterweight position, determine a second counterweight position corresponding to a second rearward stability associated with the boom orientation, determine a second crane capacity at the second counterweight position, receive an indication of the crane load from the sensor, and cause the actuator to position the counterweight at a third position between the first counterweight position and the second counterweight position dependent on the crane load, and the first crane capacity.
In some embodiments, the functions further include determine the load changing to a new load, and cause the actuator to move the counterweight to a fourth position between the first counterweight position and the second counterweight position dependent on the new load, the first crane capacity, and the second crane capacity. In some embodiments, the functions the controller performs further comprise a function to cause the actuator to maintain a set percentage of capacity at the third counterweight position.
In some embodiments, the sensor is a boom strap tension sensor and the load is a boom strap tension. In some embodiments, the sensor is a boom hoist tension sensor and the load is a boom hoist tension. In some embodiments, the sensor is a gantry compression sensor and the load is a compression of a gantry. In some embodiments, the sensor is a moment sensor and the load is a moment between an upperworks and a lower works of a crane. In some embodiments, the sensor is a ground pressure sensor and the load is a ground pressure associated with a crane outrigger.
In the following passages, different embodiments are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.
The mobile lift crane 10 includes lower works, or carbody 12, ground engaging members 14 elevating the carbody 12 off the ground; and a rotating bed 20 rotatably connected to the carbody 12 about an axis of rotation. The movable ground engaging members 14 on the crane 10 are in the form of two crawlers, only one of which can be seen from the side view of
The rotating bed 20 is mounted to the carbody 12 with a slewing ring, such that the rotating bed 20 can swing about an axis with respect to the ground engaging members 14. The rotating bed 20 supports a boom 22 pivotally mounted in a fixed position on a front portion of the rotating bed 20; a live mast 28 mounted at its first end on the rotating bed 20; and a movable counterweight unit 35 having one or more counterweights or counterweight members 34 on a support member 33 in the form of a counterweight tray. The counterweights 34 in this embodiment are provided in two stacks of individual counterweight members on the support member 33. The rotating bed 20 has a fixed rearmost portion, which will be discussed in detail below. In the crane 10, since the counterweight unit 35 is movable, it does not constitute the fixed rearmost portion of the rotating bed 20, even though when the counterweight unit 35 is moved to a rearward position the outside corner of the counterweights 34 will be the furthest from the rotational axis or centerline and thus define the tail swing of the crane 10. However, when the counterweight unit 35 is pulled forward, as in
A boom hoist system on crane 10 allows the angle of the boom 22 relative to a plane of rotation of the rotating bed 20 to be changed. The plane of rotation is typically perpendicular or nearly so to the axis of rotation. In the crane 10, the boom hoist system includes rigging connected between the rotating bed 20, the mast 28, and the boom 22. The boom hoist system includes a boom hoist drum 21 and boom hoist line 27 reeved between a sheave or sheave set on a second end of the mast 28 and a sheave or sheave set 23 on the rotating bed 20. The mast 28 is pivotally connected to the rotating bed 20, and the boom hoist rigging between the mast 28 and the boom 22 comprises only fixed length members or pendants 25 (only one of which can be seen in the side view) connected between the mast 28 and a top of the boom 22. In addition the boom hoist rigging includes multiple parts of boom hoist line 27 between sheaves 23 on the rotating bed 20 and sheaves on the second end of the mast 28. A boom hoist drum 21 on the rotating bed 20 can thus be used to take up or pay out boom hoist line 27, changing an angle of the live mast 28 with respect to the rotating bed 20, which in turn then changes an angle of the boom 22 with respect to the rotating bed 20. Alternatively, the mast 28 could be used as a fixed mast during normal crane operation, with boom hoist line 27 running between an equalizer and the top of the mast 28 to change an angle between the mast 28 and the boom 22.
A load hoist line 24 for handling a load extends from the boom 22, supporting a hook 26. The rotating bed 20 may also include other elements commonly found on a mobile lift crane, such as an operator's cab and whip line drum 29. The load hoist drum 13 for the hoist line 24 is preferably mounted on a boom butt of the boom 22, as shown in
The counterweight unit 35 is movable with respect to the rest of the rotating bed 20. In the crane 10, the rotating bed 20 includes a counterweight support frame 32, preferably in the form of a welded plate. The counterweight support frame 32 supports the movable counterweight unit 35 in a movable relationship with respect to the counterweight support frame 32. The counterweight support frame 32 comprises a sloped surface provided by flanges welded to the plate structure of the counterweight support frame 32. The counterweight unit 35 moves on the surface if the flanges, the surface sloping upwardly compared to the plane of rotation between the rotating bed 20 and the carbody 12 as the counterweight support frame 32 extends rearwardly. The counterweight tray 33 includes rollers, which rest on the flanges. The rollers are placed on the top of the counterweight tray 33 so that the counterweight tray 33 is suspended beneath the counterweight support frame 32. In the crane 10, the counterweight support frame 32 constitutes the fixed rearmost portion of the rotating bed 20. Further, the counterweight support frame 32 is supported on the rotating bed 20 in a fashion such that the moment generated by the counterweight unit 35 acts on the rotating bed 20 predominantly, and in this case only, through the counterweight support frame 32.
A counterweight movement system is connected between the rotating bed 20 and the counterweight unit 35 so as to be able to move the counterweight unit 35 toward and away from the boom 22. The counterweight unit 35 is movable between a position where the counterweight unit 35 is in front of the fixed rearmost portion of the rotating bed 20, such that the tail swing of the crane 10 is dictated by the fixed rearmost portion of the rotating bed 20 (as seen in
The counterweight movement system in the crane 10 comprises a counterweight unit movement device made up of a drive motor and a drum 42 on a rear of the counterweight support frame 32. Preferably the counterweight unit movement device has two spaced apart identical assemblies, and thus the drive motor drives two drums 42. Each assembly of the counterweight unit movement device further includes a flexible tension member that passes around a driven pulley and idler pulley (best seen in
While
The positioning of the counterweight unit 35 is controlled by a crane controller coupled with at least one sensor for determining an operating condition of the crane. The crane controller controlling the counterweight movement system, and possibly other operations of the crane, receives signals from the sensor indicating the condition (such as the boom angle), or some other function indicative of the condition (such as tension in the boom hoist rigging, which is indicative of the combined boom and load moment, or the moment of the boom 22 and load about the hinge pins of the boom 22) and controls the position of the counterweight unit 35. The position of the counterweight unit 35 may be detected by keeping track of the revolutions of drums 42, or using a cable and reel arrangement (not shown). The crane 10 using such a system will preferably comprise a computer readable storage medium comprising programming code embodied therein operable to be executed by the computer processor to control the position of the counterweight unit 35.
The exemplary embodiment 200 further includes sensors such as a length sensor 208 operably coupled to the processing unit 202. The length sensor may measure the status of crane components such as a boom length, an outrigger length, or the position of an adjustable counterweight. In the embodiment of
The processing unit 202 can be operably coupled directly to the sensor 208 as shown in
A data storage unit 214 is operably coupled to the processing unit 202 and stores computer executable instructions for execution by the processing unit 202. The computer instructions cause the processing unit 202 to perform a series of functions that will be described in more detail later. Briefly, the computer executable instruction cause the processing unit 202 to determine a first load chart for the determined boom configuration with the counterweight positioned at a first extension, a second load chart for the determined boom configuration with the counterweight positioned at a second extension, and cause the counterweight to be positioned between the first and second extension, among other typical crane functions.
In some embodiments, the processing unit 202 calculates a load chart based on the determined crane configuration. In other embodiments, a plurality of mobile crane load charts are stored in the data store 214 and the processing unit 202 selects an appropriate load chart based on the determined configuration. For example, if the data store 214 has three load charts based on a particular counterweight position, the processing unit 202 would select a load chart that is valid for determined configuration.
The method 500 begins in with the determination of the boom orientation in block 502. The boom orientation may be determined automatically using at least one sensor in communication with the control system. For example, the position of the boom may be determined through angle sensors and a length sensor. Or in other embodiments, the boom orientation may be input manually. For instance, a user may use the user interface to input at least one characteristic such as the length of the boom or the presence of a luffing jib. Or, in still other embodiments, a combination may be used such as a user entering the boom characteristics and at least one sensor detecting a changing characteristic, such as a boom angle.
In block 504, a first counterweight position is determined corresponding to a first rearward stability associated with the detected boom orientation. For example, the first counterweight position may be a position associated with a forty percent rearward stability. The first counterweight position may be determined through a calculation by the control system, or by finding a load chart having the first rearward stability with no load on the boom. In block 506, a second counterweight position is determined corresponding to a second rearward stability associated with a boom orientation. This rearward stability amount may correspond to a maximum counterweight extension with no load on the boom. For example, if regulations require a rearward stability of seventy percent or less, the second counterweight position may correspond to a rearward stability of seventy percent.
In block 508, a first crane capacity is determined based on the counterweight being at the first counterweight position. For example, the crane controller may calculate the capacity at the first counterweight position, or look up the maximum capacity based on a load chart. In block 510, a second crane capacity is determined based on the counterweight being at the second counterweight position.
In block 512 a load on the crane is determined by the control system. For example, the tension in a hoist line may be measured, a load on a backstay may be measured, or moment of the boom may be measured. In block 514, the counterweight is positioned at a third position between the first counterweight position and the second counterweight position. The position is dependent on the boom load and the first crane capacity. In some embodiments, the position may further be dependent on the second crane capacity. For example, the third counterweight position may be a function of the percentage of the measured load relative to the maximum load at the first position. As the measured load approaches a set amount of the maximum load at the first position, the third position moves a proportional amount. Or in other embodiments, the position may be further dependent on the second crane capacity, such that as the measured load approaches the second crane capacity, the counterweight moves a proportional amount.
In block 516, the control system detects a change of the load to a new load and in response, in block 518 the counterweight is moved to a fourth position between the first counterweight position and the second counterweight position dependent on the new load and the first crane capacity, and possibly the second crane capacity. The load may correspond to a set percentage of the first crane capacity and the new load may be the set percentage of a third capacity associated with the third percentage of the first capacity. For example, the counterweight may move such that the crane operates at fifty percent capacity, with capacities less than fifty percent resulting in the first counterweight position and capacities greater than fifty percent resulting in the second counterweight position.
The load detected by the control system may be a boom strap tension, a boom hoist tension, a compression of a gantry supporting the counterweight, a load moment between an upper works and a lower works of a crane, a load moment between a crane carbody and a crane crawler, and a ground pressure associated with a crane outrigger. Each of these techniques for measuring a load as well as others are well known in the art.
Embodiments are further directed to a system for controlling the position of a counterweight on a crane. The system includes an actuator, such as a hydraulic cylinder or rack and pinion. The actuator is configured to change a horizontal position of a counterweight relative to a crane body. At least one sensor is configured to measure a crane load. The crane load may be one of, or a combination of, boom strap tension, a boom hoist tension, a compression of a gantry, a load moment between an upperworks and a lower works of a crane, a load moment between a crane carbody and a crane crawler, and a ground pressure associated with a crane outrigger. The system further includes a controller, such as the controller of
It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. For example, the crane controller could be separate from other control systems of the crane, or it may be integrated with further functionality. Additionally, while not described in detail, one of ordinary skill in the art will recognize that the different embodiments may be used in combination with one another.
The present patent document claims the benefit of the filing date under 35 U.S.C. §119(e) of Provisional U.S. Patent Application Ser. No. 62/141,013, filed Mar. 31, 2015, which is hereby incorporated by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5598935 | Harrison | Feb 1997 | A |
| 20050098520 | Frankenberger et al. | May 2005 | A1 |
| Number | Date | Country |
|---|---|---|
| 29924978 | Aug 2007 | DE |
| H1149484 | Feb 1999 | JP |
| WO 9421549 | Sep 1994 | WO |
| Entry |
|---|
| European Search Report for related European Application No. 16163096.7, dated Aug. 31, 2016 (10 pages). |
| Number | Date | Country | |
|---|---|---|---|
| 20160289047 A1 | Oct 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62141013 | Mar 2015 | US |
